Basil blooming? Don’t let it, if you want to keep that harvest coming.
If you allow the plant to flower, it will tell itself, "I've fulfilled my life's purpose by making seed, so I can just stop growing." So check every day, and pinch the flowers as soon as they appear. In areas with a long growing season, you can refresh plants even more by trimming the tips and fertilizing with fish emulsion or Miracle-Gro® LiquaFeed® Tomato, Fruits & Vegetables Plant Food (follow label directions). Have more basil than you can use? Put a few sprigs in a small vase to perfume the kitchen.
With a little attention and care (and a lot of pinching!), your basil can continue to produce a nice harvest until cold weather arrives. Basil will turn brown at the first sign of frost. So when a freeze is in the forecast, consider harvesting the remaining leaves and making pesto, then freezing it for ready access to that fresh basil flavor.